GitLab

* 1) Fixed Predictor lifecycle
2) Fixed Boosting trees initialization

#5482

* Added tests for LGBM_BoosterPredictForMat in Contrib mode

* #6778 Reverted indentation to 4 spaces

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Co-authored-by: James Lamb <jaylamb20@gmail.com>
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>